Pressure switch with diaphragm and adjustable contact

ABSTRACT

A flexible polymeric-metal laminate diaphragm is used in a pressure responsive switch for engaging and disengaging switch terminals in accordance with periodic changes in pressure.

I United States Patent [1 1 7/1960 Dodge Alvarez [451 June, 4, 1974PRESSURE SWITCH WITH DIAPHRAGM 3,594,522 7/1971 Colglazier 200/83 N xAND ADJUSTABLE CONTACT 3,689,719 9/1972 Phillips et al. 200/83 X [75]Inventor: WiIliam Alvarez, Placentia, Calif. FOREIGN PATENTS ORAPPLICATIONS Assignee: Jonathan Manufacturing p y, l,0l3,778 8/1952France 200/83 N Fullerton, Calif. I OTHER PUBLICATIONS [22] Filed: Oct.17, 1972 IBM Technical Disclosure, Pressure Sensitive Elastic vDiaphragm Switch"; Vol. 14, No. 3, p. 878; 8/1971;

[2]] Appl DeBeaumont et al. I

[52] US. Cl. 200/83 N, 200/8l.9 R 7 Primary Examiner-Robert K. Schaefer[5]] Int. Cl. 01h 35/34 Assistant Eraminer--Gerald P. Tolin [58] Fieldof Search......... 200/83-N, 8-1.9 R, 159 B, r

. 2.00/86 A 57 ABSTRACT UNITED STATES PATENTS gaging switch terminals inaccordance with periodic 1,998.82! 4/1935 Rockwell 200/83 N ux Changesin pressure 2,768,26l 10/1956 Mathisen I 200/83 N 2,944,558 ZOO/81.9 RX'1 Claim, 2 Drawing Figures a PRESSURE swircii'wiru DIAPHRAGM ANDADJUSTABLE CONTACT BACKGROUND OF INVENTION being those in which aflexible diaphragm is exposed to fluid pressure to be sensed which, ifexcessive, deflects the diaphragm which, in turn, activates suitablemechanism arranged to close or open an electric circuit, as the case maybe. Various types of diaphragms are used such as for example, single ordouble thin sheet metal discs of the snap-action type as disclosed inU.S. ,Pat. No. 3,585,3 28; diaphragms of the type requiring resetstructure as shown in U.S. Pat. No. 3,579,284, and U.S. Pat. No. 3,29I932; orspring-Ioaded diaphragms of the type disclosed in U.S. Pat. No.3,600,535. Moreover, in substantially every instance, the diaphragms aredesigned either to carry or activate auxiliary members for energizing anelectric circuit. Thus these and similar diaphragm-type switches of theprior art-embody a mul- 'tiplicity of components including many movingparts,

some of which'are of relatively heavy construction. As

a consequence, these switches are relatively slow acting and relativelyinsensitive to slightchanges in pressure.

It is desirable, however, for certain applications such as, for example,on-off switches, unit counters and the like, to provide a pressureresponsive switch which is sensitive to minimal pressure differentialsand is ex- The present invention achieves these objectives by phragm toestablish relative negative pressure or vacuum, as the case may be,which deflects the diaphragm in the reverse direction therebydisengaging its coppersurfaced side from contact with the switchterminal means.

In the normally off switch illustrated herein, the diaphragm is mountedin a chamber within a dielectric body member having air passagesarranged to conduct air to the dielectric side of the diaphragm and fromthence to the atmosphere. The copper surfaced side of the diaphragm orcurrent-conducting side as it is sometimes hereinafter called, isarranged opposite and spaced from one or more switch terminal meansproviding a pressure responsive switch having no moving parts other thanthe flexible'diaphragm itself which is characterized by extremely lightweight construction and hence is not only sensitive to very smallchangesin pressure, as for example, a pressure differential of as low as l/4inch water, but substantially immediately responsive thereto to effectenergization of electric circuitry. More particularly, the pressureresponsive electric switch of this, invention is characterized by'theuse of a thin flexible diaphragm approximately 0.0025 inches thickcomprising a polymeric-metal laminate and in particular a dielectricplastic sheet surfaced on one side with a metalsuch as copper andmounted in the switch assembly in a manner to permitthe diaphragm toflex freely and in so doing deflect its coppersurfaced side into andfrom contact with suitable switch terminal means in response tovariations in pressure acting on the diaphragm. These variations inpressure are effected by a fluid and in particular by a stream of airwhich normally flows past the diaphragm and in so doing subjects iteither to minimal positive pressure or negative pressure. as the casemay be.

Assuming the switch is designed to be normally off, as hereinafterdescribed, to activate the switch to its on" position, the flow of airpast the diaphragm is momentarily restricted or stopped, as the case maybe, whereupon the pressure of air against the diaphragm is increasedsufficiently to deflect the coppersurfaced side of the diaphragm intocontact with the switch terminal means. Upon releasing the air the pressure on the diaphragm is lowered sufficiently at the diamounted in thebody member. A source of air is connected to the air passages andarranged normally to provide a steady flow of air through the passagesfrom which the air exits to the atmosphere. The switch is made tofunction as an on-off" switch or as a unit counting device bysuccessively closing and opening theair exit passage to theatmosphere-and due to the relative simplicity of construction .and thelight weight of the diaphragm, the latter may be made to respond withgreat rapidity to the closing and opening of the exit passage.

While the embodiment of the invention shown herein and hereinafterdescribed comprises a switch assembly adapted to be normally off and tobe turned on periodically it will be understood that the invention isdesigned to operate in reverse to be normally on and to be turned offperiodically.

DESCRIPTION OF DRAWINGS PREFERRED EMBODIMENT OF THE INVENTION Referringto FIG. 1, the pressure responsive switch assembly will be seen tocomprise a body member indicated generally at 10. The latter may takethe shape of a substantially rectangular or disc-shaped block formed ofa dielectric material such as a polymeric plastic or the equivalent, andis fashioned from two separate but complimentary parts, indicated at 11and l2respectively secured together at a common interface 13 by suitablefastening means such as machine screws as il- .Iustrated at 14.

The inner surface of the part 11 at interface 13 is provided with arelatively shallow recess 15 dimensioned to accomodate a major portionof the flexible diaphragm hereinafter described. Part 11 is alsoprovided with an internally threaded aperture 16 which extends inwardlyfrom the outer face of part II on an axis substantially coincident withthe center of the recess 15 the diameter of the aperture 16 being suchas to accommodate an externally threaded stud screw 17 which serves as aswitch terminal. To this end, the latter is threaded into the aperture16 sufflciently that the inner end of the stud screw 17 extends a shortdistance into the recess 15; and is provided with a lock nut 18 by whichthe inner endof the stud screw may be fixedly secured in a selectedadjusted position in the recess 15.

A second switch terminal is provided in part 11 and, as indicated at 19,may take the form of 'a machine screw threaded into an aperture adjacentto the outer edge of the part 11 and arranged to extend therethrough tothe interface 13. The machine screw 19 is also provided with a lock nutas at 20 for locking the screw in adjusted position. Both the switchterminal 17 and 19 are provided with wire leads 21- 21 adapted to beconnected to electric circuitry including a source of electric energy,and auxiliary motor driven equipment (not shown).

I The block 12, which is adapted to be secured to tively, each ofrelatively small diameter. The passage 22 extends entirely through part12 from its inner face, as defined by interface 13, to its outer orbottom face, as seen in FIG. 1, its longitudinal axis beingsubstantially in allignment with the longitudinal axis of the stud screw17. Passage or gallery 23 is drilled or otherwise formed in part 12substantially intermediate its inner face and. its bottom face and atsubstantially right angles to passage 22. The inner end of passage 23intersects passage 22 while its outer end is enlarged by an internallythreaded counterbore 24 formed in the corresponding side wall of part12. The counterbore 24 is adaptedto receive fitting 25 by which an airhose 26 is connected to passage 23. i

Mounted between the two parts 11 and 12 of the dielectric block at theinterface 13 thereof is a flexible diaphragm 27. The latter comprises athin sheet of dielectric material, one side of which is surfaced with acurrent conducting metal such as copper. A particularly satisfactorydiaphragm is a flexible polyimidemetal laminate, comprising a thin sheetof a dielectric polymid polymer coated on one side with copper. Typicallaminates are those used as electric .circuit boards and the like asdisclosed in US. Pat. Nos. 3,179,614 and 3,582,458.

In the embodiment of FIG. 1, diaphragm 27 is dimensioned to span therecess .15 and is sandwiched securely between the inner faces of theupper and lower parts 11 and 12 respectively of the dielectric block 10with a fluid tight joint. When so assembled, the recess constitutes adiaphragm chamber. The copper surface of the diaphragm is disposeduppermost so as to be opposite the inner end of the terminal stud screw17 but spaced therefrom; and for permanentengagement by the inner end ofthe terminalscrew 19.

t The operation of the pressure responsive switch of FIG. 1 is asfollows: a gas, such as air, is continuously supplied to the passage 23,via air pipe 26 and fitting 25, at relatively low pressure, as forexample, 2.5 inches water. The air passes through the passage 23 andpassage 22 and escapes to the atmosphere via of air exit orifice 28.Since the diameters of the passages and orifice are relatively small,slight back pressure is created within the passage 22, which causes thediaphragm to partially deflect toward the inner end of the terminal studscrew 17 but insufficiently to contact it the space therebetween beingof the order of a few thousandths inches. Upon closing air exit orifice28, the back pressure in passage 22 is increased thereby defleeting thediaphragm into contact with the terminal stud screw 17 and providingelectrical continuity be tween stud screw 17 and terminal screw 19 viaof the copper surface of the diaphragm. As soon as air exit orifice 28is uncovered, the back pressure is reduced and the partial vacuumcreated by the venturi effect at the intersection of the passages 22 and23 returns the diaphragm to its original position thus opening theelectric path between terminals 17 and 19.

Because of its simplicity of construction and the light weight of thediaphragm, the latter has been found to respond at a rate in the rangefrom O to 45 pulsations/- sec. to alternate closing and opening of theair exit orifice 28 and hence the assembly is extremely useful as arapidly acting onofF switch.

Referring to the modification shown in FIG. 2 wherein elements similarto those of FIG. 1 are similarly identified, the pressure responsiveswitch is designed specifically as a unit counter. This switch assembly,indicated generally at 30, is preferably rectangular in cross-sectionand comprises two parts 31 and 32, each formed of a suitable dielectricmaterial and secured together by fastening means such as machine screwsor the like as indicated at 33. The part 31 is provided on its innerface with a shallow rectangular or circular recess 34. At the center ofthe recess 34 a small aperture 35 is drilled through the reduced sectionof the part 31 to the outer face thereof. Additional apertures aredrilled through the reduced section of part 31 on opposite sidesrespectively of the central aperture 35 to accommodate round headedmachine screws 36 36 the heads of which are located in the recess 34.

Adjusting nuts 37 37 and lock nuts 38 38 are threaded on the outerextremities of the machine screws for securing the latter inpredetermined adjuste'd positions and for attaching wire leads 39 39thereto.

The machine screws 36 36 thus serve as switch terminals of electriccircuitry connected to the wire leads 39 39.

The part 32 of the dielectric block 30 comprises a substantiallyrectangular body portion, the bottom of which is characterized byintegral forwardly and rearwardly extending shoes 40 40, the soles ofwhich form a continuous substantially smooth surface 41 for engagementby unit articles to be counted.

Referring to the upper portion of part 32, its face, 0pposite that ofthe recessed part 31, is provided with a recess 42 somewhat deeper thanthe recess 34 in part 31 but dimensioned to compliment the latter sothat when the parts 31 and 32 are secured together, the recesses 34 and42 form a single chamber for accomodating the flexible diaphragm 27. Asin the assembly of FIG. 1, the diaphragm is dimensioned to span thechamber and is held securely therein by being sandwiched between the twoparts 31 and 32 the latter being securely held together with a fluidtight joint by machine screws 33.

A passage or gallery 43, of relatively small diameter, is drilledsubstantially vertically, as seen in FIG. 2 through part 32 from top tobottom. Its upper end is enlarged by an internally threaded counterbore24 for attaching a fitting 25 and air hose 26 thereto, while the lowerend of the passage 43 forms an air exit orifice 44 in the sole 41 ofsaid shoes.

A second passage identified at 45, also of relatively small diameter, isformed in part 32 substantially at right angles to passage 43 andconnects the latter to the recess 42 substantially centrally thereof.

The operation of the switch assembly of FIG. 2 is as follows: A gas,such as air, under positive pressure of the order of from 2.5 to 5lbs/square inch is introduced continuously to passage 43. As long as airexit orifice 44 is open, the gas flows past passage 45 to the atmosphereand in so doing, creates a venturi effect, i.e., negative pressure inpassage 45, which, in conjunction with the atmospheric pressure actingon the opposite side of diaphragm 27 (because of aperture 35) holds thecurrent conductive side of diaphragm away from the terminal contacts 3636. However, as soon as the air exit orifice 44 is closed pressurizedair enters passage 45 and creates positive pressure on the corre-.sponding side of the diaphragm, which pressure exceeds the atmosphericpressure on the current conducting side thereof. As a consequence, theflexible diaphragm is deflected to engage its current conducting sidewith the switch terminals, as indicated by the dotted lines, to provideelectrical continuity from one to the other via the copper surface ofthe diaphragm.

In the embodiment shown herein, the air exit orifice 44 is adapted to besuccessively opened and closed by unit articles, indicated at 46,'fed'forwardly continuously against the shoe 4] of the assembly past theorifice 44.Thus as each article approaches and closes the orifice 44,the diaphragm is flexed into contact with the switch terminals therebyenergizing the switch assembly; and as the articles pass beyond theorifice 44, the diaphragm is withdrawn from contact with the switchterminals and the switch is deenergized. The alternate energizing anddeenergizing of the switch assembly may operate electric circuitryincluding counting means whereby the articles may be continuouslycounted.

in the embodiment of the invention shown in each of H68. 1 and 2 theswitches are designed as normally of that is to say the currentconducting side of the flexible diaphragm is normally out of contactwith the switch terminal means and is moved into contact by applying airpressure to the opposite side of the diaphragm, It would be understood,however, that either one of the switches of FIGS. 1 and 2 may bemodified in a manner to be normally on by the obvious and relativelysimple expedient of adjusting the switch terminal means normally toengage the current conduct- 6 ing side of the diaphragm and introducingthe pressurized air against the same side of the diaphragm to move itscurrent conducting side away from the switch terminal means therebyopening the switch which modifications are contemplated within the scopeof the present invention.

The invention may be carried out in other specific ways than thoseherein set forth without departing from the spirit and essentialcharacteristics of the invention, and the present embodiments, aretherefore, to be considered in all respects as illustrations and notrestrictive and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

l claim:

1. A pressure responsive electric switch assembly comprising adielectric body member, a chamber in said body member, adjustable switchterminal means comprising a metal terminal post threadedly engaged insaid dielectric body member with one end extending into said chamber, athin flexible diaphragm arranged in said chamber said diaphragmcomprising a dielectric polymer approximately 0.0025 inches thick andsurfaced on the side opposite said adjustable switch terminal means witha coating of metal for contact therewith, and two air passages in saidbody member, one air passage opening at one end into said chamber andthe opposite end of said one air passage having an unrestricted openingdirectly exposed to the atmosphere, the 2nd air passage intersectingsaid one air passage,

' said Znd air passage being connected at one end to a continuous sourceof pressurized air and at the other end closed at a point beyond theintersection of the passages, the said one air passage exposing one sideof said flexible diaphragm intermittently to positive and negative airpressure in accordance with the non-flow and flow respectively ofair'from said unrestricted opening to the atmosphere whereby the metalsurfaced side of said diaphragm is selectively moved into and fromelectrical contact with said adjustable switch terminalmeans.

1. A pressure responsive electric switch assembly comprising adielectric body member, a chamber in said body member, adjustable switchterminal means comprising a metal terminal post threadedly engaged insaid dielectric body member with one end extending into said chamber, athin flexible diaphragm arranged in said chamber said diaphragmcomprising a dielectric polymer approximately 0.0025 inches thick andsurfaced on the side opposite said adjustable switch terminal means witha coating of metal for contact therewith, and two air passages in saidbody member, one air passage opening at one end into said chamber andthe opposite end of said one air passage having an unrestricted openingdirectly exposed to the atmosphere, the 2nd air passage intersectingsaid one air passage, said 2nd air passage being connected at one end toa continuous source of pressurized air and at the other end closed at apoint beyond the intersection of the passages, the said one air passageexposing one side of said flexible diaphragm intermittently to positiveand negative air pressure in accordance with the non-flow and flowrespectively of air from said unrestricted opening to the atmospherewhereby the metal surfaced side of said diaphragm is selectively movedinto and from electrical contact with said adjustable switch terminalmeans.